The cult of Lugh was a latecomer into Ireland, introduced by Gaulish or British refugees fleeing from the advancing Roman armies. The name Tailtiu is not Irish in origin but from the Welsh telediw, which means ‘well-formed’. Lugh is often described as a pan-Celtic deity and identified with the continental Lugus, Lud in England and Llew in Wales. His name is probably related to the Proto-Celtic *lug- meaning ‘oath’, and all the indications are that he was neither a god of agriculture nor the sun, as is often claimed. The central part of Lugh’s story is the
rivalry between him and his grandfather Balor and the battle for supremacy and kingship between the Tuatha de Danaan and the Formorians. The pattern of Lugh’s tale is a common mythic theme and begins with a prophecy that the grandson (or son) of the king will overthrow him.
Mason, Paul; Franklin, Anna . Lughnasa (The Eight Festivals Book 2) (Kindle Locations 311-313). Lear Books. Kindle Edition.